Linnaeus, 1763: 413 Robber flies (Insecta: Diptera: Asilidae) of Wyoming, USA with keys to genera and species Lavigne, Robert J. Dennis, Steve Zootaxa 2019 2019-08-30 4662 1 1 126 (Linnaeus) Linnaeus [151,467,692,719] Insecta Asilidae Nerax GBIF Animalia Diptera 37 38 Arthropoda species aestuans     Asilus aestuans  Linnaeus, 1763: 413.   Recognition characters:Grayish-black species; length 18–20 mm; mystax black above, white below with few black bristles on oral margin; bristles and setae of mesonotum largely black with white setae posteriorly; meral bristles black in both sexes; scutellar setae white, marginal bristles black; males with abdominal segments 5–7 silvery white pollinose, sternite 8 produced apically with long black setae; legs, femora black, tibiae brown fading to black apically.  Distribution:Recorded from Wyomingby Cole (1969)(as  Efferia aestuans); Fisher & Wilcox (1997)(as  Efferia aestuans); Geller-Grimm (2018).  Habitat:Sagebrush steppe and wheatgrass-needlegrass shrub steppe shrub and grassland, and grama-needlegrass-wheatgrass, grama-buffalo grass, and wheatgrass-needlegrass grassland vegetation types.  Ethology:Nothing known.  Prey:None known.